Fluid control devices include various categories of equipment including control valves and regulators. Such control devices are adapted to be coupled within a fluid process control system such as chemical treatment systems, natural gas delivery systems, etc., for controlling the flow of a fluid therethrough. Each control device defines a fluid flow-path and includes a control member for adjusting a dimension of the flow-path. For example, FIG. 1 depicts a known regulator assembly 10 including a valve body 12 and an actuator 14. The valve body 12 defines a flow-path 16 and includes a throat 18. In FIG. 1, the regulator assembly 10 is configured in a flow-up configuration. The actuator 14 includes an upper actuator casing 20, a lower actuator casing 22, and a control member 24. The control member 24 is disposed within the upper and lower actuator casings 20, 22 and is adapted for bi-directional displacement in response to changes in pressure across the regulator assembly 10. So configured, the control member 24 controls the flow of fluid through the throat 18. Additionally, as is depicted, the regulator assembly 10 includes a seat ring 26 disposed in the throat 18 of the valve body 12. When the outlet pressure of the valve body 12 is high, a sealing surface 28 of the control member 24 may sealingly engage the seat ring 26 and close the throat 18. This prevents the flow of fluid through the regulator 10.
FIG. 1 depicts the regulator assembly 10 equipped with one known seat ring 26. The seat ring 26 includes a generally ring-shaped body secured in the throat 18. The seat ring 26 includes a seating surface 30 and an orifice 32. As mentioned, the seating surface 30 is adapted to be engaged by the sealing surface 28 of the control member 24 when in a closed position to prevent the fluid from flowing through the valve body 12. The seat ring 26 depicted in FIG. 1 further includes a rounded or tapered surface 34. The rounded or tapered surface 34 serves to streamline the flow of the fluid through the orifice 32. Additionally, it can be seen in FIG. 1 that a diameter of the seating surface 30 is substantially equal to both a diameter of the orifice 32 of the seat ring 26, as well as a diameter of the sealing surface 28 of the control member 24. Therefore, as fluid flows through the valve body 12, it flows from the left of the valve body 12, as depicted in FIG. 1 and up through the throat 18 via the orifice 32 in the seat ring 26. Then, the fluid deflects off a lower surface of the control member 24 including the sealing surface 28, and out to the right of the valve body 12 of FIG. 1.
One shortcoming of the above-described regulator assembly 10 is that the orifice 32 includes a diameter that is close to a diameter of the sealing surface 28 of the control member 24. Often times, such a pressure regulator assembly 10 is implemented into a fluid delivery system for delivering natural gas. Natural gas tends to include debris or particulate matter that, when traveling through the regulator assembly 10, can damage the regulator assembly 10. For example, as debris or particulate matter traveling under high pressure travels through the orifice 32 in the seat ring 26, it impacts the sealing surface 28 of the control member 24. Typical sealing surfaces 28 are constructed of rubber. Upon impact, the debris or particulate matter can damage the rubber and thereby effect the performance of the regulator.